[1.6.x] Fixed #21284 -- Prevented KeyError swallowing in fetch_command

Thanks wildfire for the report.

Backport of 3514bcb251 from master.

django/core/management/__init__.py

@@ -257,8 +257,10 @@ class ManagementUtility(object):
         appropriate command called from the command line (usually
         "django-admin.py" or "manage.py") if it can't be found.
         """
+        # Get commands outside of try block to prevent swallowing exceptions
+        commands = get_commands()
         try:
-            app_name = get_commands()[subcommand]
+            app_name = commands[subcommand]
         except KeyError:
             sys.stderr.write("Unknown command: %r\nType '%s help' for usage.\n" % \
                 (subcommand, self.prog_name))

tests/admin_scripts/tests.py

@@ -1004,28 +1004,24 @@ class ManageMultipleSettings(AdminScriptTestCase):
         self.assertOutput(out, "EXECUTE:NoArgsCommand")
 
 
-class ManageSettingsWithImportError(AdminScriptTestCase):
-    """Tests for manage.py when using the default settings.py file
-    with an import error. Ticket #14130.
+class ManageSettingsWithSettingsErrors(AdminScriptTestCase):
+    """
+    Tests for manage.py when using the default settings.py file containing
+    runtime errors.
     """
     def tearDown(self):
         self.remove_settings('settings.py')
 
-    def write_settings_with_import_error(self, filename, apps=None, is_dir=False, sdict=None):
-        if is_dir:
-            settings_dir = os.path.join(test_dir, filename)
-            os.mkdir(settings_dir)
-            settings_file_path = os.path.join(settings_dir, '__init__.py')
-        else:
-            settings_file_path = os.path.join(test_dir, filename)
+    def write_settings_with_import_error(self, filename):
+        settings_file_path = os.path.join(test_dir, filename)
         with open(settings_file_path, 'w') as settings_file:
             settings_file.write('# Settings file automatically generated by admin_scripts test case\n')
             settings_file.write('# The next line will cause an import error:\nimport foo42bar\n')
 
-    def test_builtin_command(self):
+    def test_import_error(self):
         """
         import error: manage.py builtin commands shows useful diagnostic info
-        when settings with import errors is provided
+        when settings with import errors is provided (#14130).
         """
         self.write_settings_with_import_error('settings.py')
         args = ['sqlall', 'admin_scripts']
@@ -1034,9 +1030,10 @@ class ManageSettingsWithImportError(AdminScriptTestCase):
         self.assertOutput(err, "No module named")
         self.assertOutput(err, "foo42bar")
 
-    def test_builtin_command_with_attribute_error(self):
+    def test_attribute_error(self):
         """
-        manage.py builtin commands does not swallow attribute errors from bad settings (#18845)
+        manage.py builtin commands does not swallow attribute error due to bad
+        settings (#18845).
         """
         self.write_settings('settings.py', sdict={'BAD_VAR': 'INSTALLED_APPS.crash'})
         args = ['collectstatic', 'admin_scripts']
@@ -1044,6 +1041,13 @@ class ManageSettingsWithImportError(AdminScriptTestCase):
         self.assertNoOutput(out)
         self.assertOutput(err, "AttributeError: 'list' object has no attribute 'crash'")
 
+    def test_key_error(self):
+        self.write_settings('settings.py', sdict={'BAD_VAR': 'DATABASES["blah"]'})
+        args = ['collectstatic', 'admin_scripts']
+        out, err = self.run_manage(args)
+        self.assertNoOutput(out)
+        self.assertOutput(err, "KeyError: 'blah'")
+
 
 class ManageValidate(AdminScriptTestCase):
     def tearDown(self):